Scaffold stair unit



Aug. 28, 1956 A. ANDERSON 2,760,707

SCAFFOLD STAIR UNIT Filed July 9; 1951 INVENTOR. ARVID A. AnoeasomATToRNEY SCAFFOLD STAIR UNIT Arvid A. Anderson, Milwaukee, Wis.,assiguor to Safway Steel Products, Inc., Milwaukee, Wis., a corporationof Wisconsin Application July 9, 1951, Serial No. 235,819

1 Claim. (Cl. 228-45) This invention relates to a stair unit for use inprefabricated sectional scaffolding of the type employing standardizedframe sections which may be interconnected to form a rigid structure ofthe desired size.

In the past ladders, either separate or integral with the frame members,have been employed to afford access to the various levels in thescaffolding. In addition to the obvious objection that ladders arerelatively difi"1- cult to climb, it is impractical to attempt to carrya load when climbing a ladder. Recently there have been some effortsdirected to provision of a scaffold stairway, but all designs thus faradvanced have been objectionable for lack of versatility, erectiondifliculties and inefficient design so far as use and materials areconcerned. The present invention overcomes past objections.

An object of this invention is to provide a simple, economical stairwayunit for scaffolding.

Another object is to provide a stair unit which may be rapidly erected.

Another object is to provide a stair unit for scaffolding which isversatile and permits of a number of variations in erection to meet theneeds of the particular installatron.

A further object is to provide a stair unit which includes clamp unitsfor securing the unit to the scaffolding in a safe manner.

Still another object is to provide a clamp which normally holds thestair unit to the scaffolding and may be rendered inoperative tofacilitate erection.

Other objects and advantages will be pointed out in, or be apparentfrom, the specification and claims, as will obvious modifications of thesingle embodiment shown in the drawings, in which:

Fig. l is a side elevation of the stair unit with a portion ofscaffolding shown in dot-dash lines;

Fig. 2 is an elevation as viewed from the right of Fig. 1;

Fig. 3 is a side elevation showing the manner of erecting the stairunits in scaffolding;

Fig. 4 is an end view of Fig. 3;

Fig. 5 is a plan view of Fig. 3;

Fig. 6 is a side elevation of the clamp partly in section; and

Fig. 7 is a plan view of the clamp of Fig. 6.

Referring to the drawings in detail, the stair unit 10 includes a pairof stringers 12, 12 provided with a clamp 14 at each end. The clamps aredesigned to permit the stair unit to be rigidly fixed to the horizontalmembers 16, 16 of the scaffold end frames 18 except that the bottom ofthe lower stair unit (Figs. 3 and 4) is connected to a horizontal member20 mounted on the standard end frame for this purpose. It will be notedthat the stair unit is bent near its lower end so platform 22 will behorizontal when the unit is mounted between end frames which areinterconnected by means of scissors type cross braces 24 which alsoserve to properly space the end frames.

Usually the stair units would be assembled as shown in Figs. 3 and 4where the units are staggered and reatent quire changing direction atthe end of each flight. Since the platform or stair landing is adjacentthe top stair tread 26 when thus erected it is a convenient and easyascent. Where the scaffold permits and it is desired the stair units maybe assembled to provide a practically straight stairway (with thelanding at each flight) by mounting one stringer between the stringersof the adjacent unit with successive units passing through thescaffolding in the same general direction. When properly assembled inthis manner ascent may be made without changing direction at eachlanding. It will be appreciated that each unit will be out of alignmentwith adjacent units by the stringer thickness (usually no more than twoinches) but this is of little importance.

The provision of clamps 14 at each end of each stringer 12 makes suchversatility in erection possible. Each clamp has a head 28 provided witha U-shaped saddle 3t] and carried on a shank 32 which projects into thetubular stringer. The stringer is struck inwardly at diametricallyopposed points to provide semi-elliptical tongues 34 to engage notches36 in the shank and fix the clamp in the end of the stringer. A shoulderis provided between the clamp head and shank so the stringer may buttthis point. Latch pin 38 is reciprocally mounted in the head and urgedby spring 40 to project partially across the saddle opening totangentially engage horizontal frame member 16. When thus clamped themember 16 may not be withdrawn until pin 38 is pulled back by means ofactuator 42 pivotally mounted on the end of the latch pin by means ofshaft 44. The actuator is provided with a forked nose 46 and may berocked in the direction shown by the arrow in Fig. 6 to bring the noseinto alignment with the axis of shaft 44 and the longitudinal axis ofpin 38 as shown in dotted lines in Fig. 6. As may be seen, this movementpulls latch pin 38 back to open the saddle. Since the spring pull isineffective in this position the pin remains withdrawn until theactuator is started back to its original position, at which time thespring will drive the pin out.

The ability to open the clamp in this manner greatly facilitateserection of the unit. All the clamps are first opened and the lowerclamp may then be placed on the member 16, with the unit in a generallyvertical position. The pins may then be released (a kick on the actuatorwill usually suffice) and the unit pivoted until the upper clamp seatson the member 16. The worker may then climb the steps and release theupper latch pins to complete the installation. This method avoids theneed for supporting the weight of the unit at an awkward angle but itwill be appreciated that all clamps could be seated first and that othermethods may be worked out. Taking this unit down is also a simple matterdue to the ability to hold the clamps open.

As shown in Figs. 3 through 5 these stair units afford access to plank48. Planks may be provided at all or any desired level in thescaffolding. The present structure immediately suggests a modificationessentially amounting to inverting the unit so the platform is at thetop (with the clamp being turned so the saddle still faces downwardly)as if the drawings were inverted. Other changes will of course occur tothe art and for this reason the present invention is to be limited onlyby the scope of the claim.

I claim:

A stair unit for use in scaffolding of the type including horizontallyand vertically spaced parallel horizontal members, comprising a pair ofparallel stringers adapted to be connected to vertically andhorizontally spaced scaffold members, a quick release clamp at each endof each stringer for releasably securing the stringers to the members, ahorizontal platform interconnecting said stringers adjacent one end ofthe pair of stringers,

and a plurality of treads interconnecting said stringers, along theremainder of the stringers, each said clamp comprising a U-shaped saddlethe open end of which is adapted to face downwardly to receive ahorizontal member of the scaffold frame When the unit is properlypositioned in the scaffolding and includes a spring projected latch pinfor at least partially closing the open end of said saddle together withmanually operable pin retracting means for withdrawing the pin to aposition permitting entrance of a scalfold member into the saddle, themanually operable pin retracting means is mounted for pivotal movementabout a transverse axis carried by the pin, said pin retracting meansincluding a cam portion eccentrically disposed with respect to said axisand adapted to ride on a cooperating surface provided on the saddlewhereby when the pin retracting means is rotated on said axis, the pinis retracted against the bias of said spring, means for maintaining thepin retracting means in a position to retain the pin in retractedposition, said pin retracting means being adapted for quick release byreverse rotation thereof to cause the pin to be projected to normalposition by said spring.

References Cited in the file of this patent UNITED STATES PATENTS KnightMay 6, 1884 Thomson May 6, 1890 Richards July 18, 1893 Chamberlain Feb.17, 1903 Lillow Jan. 8, 1907 Duncon et a1. Jan. 19, 1909 McLeran Jan.28, 1913 Auchu June 8, 1915 De Veau et a1. Dec. 15, 1931 Fee Oct. 11,1932 Bailey Jan. 23, 1934 Uecker Aug. 2, 1938 Jaenichen July 23, 1940Roney et a1. Jan. 19, 1943 Johnson et al Mar. 23, 1948 Wyscoki Nov. 15,1949 FOREIGN PATENTS Austria Nov. 26, 1906

